1. Field of the Invention
The present invention relates to a hose having a structure that a metal plating layer is formed in resin layers, and a method of producing the same.
2. Description of the Art
For example, as a fuel hose for automotive vehicles, Japanese Unexamined Patent Publication No. 8-269723 proposes a hose having a metal plating layer having low permeability to fuel as an intermediate layer formed in a peripheral wall (resin layer) constituting the fuel hose in order to improve low permeability to fuel.
Such a hose having a metal plating layer incorporated therein is produced as follows. A tubular resin inner layer is extrusion molded using a resin containing talc. An outer peripheral surface of the resin inner layer is etched using an etching solution containing a palladium catalyst. By this etching, talc present on the outer peripheral surface of the resin inner layer is removed to form depressed portions of the removed traces, and at the same time, palladium is fixed to the outer peripheral surface (including the surface of the depressed portions) of the resin inner layer. A metal plating layer is formed on the outer peripheral surface of the resin inner layer by electroless plating. The metal plating layer is further strongly adhered to the outer peripheral surface of the resin inner layer by an anchor effect due to the depressed portions. Thereafter, a tubular resin outer layer is extrusion molded on an outer peripheral surface of the metal plating layer. Thus, the hose is produced.
Specifically, in forming the metal plating layer in the above hose, talc is added to a material for forming the resin inner layer in order to exhibit the anchor effect.
However, a resin member (the resin inner layer) containing talc is easy to break. For example, when fitting the above hose or press inserting the hose in a connector, there is the possibility that the resin inner layer breaks. Further, in a method of producing such a hose, it takes much time (about several ten minutes) in the above-described etching and palladium fixing, and in-line production is difficult. In addition, the etching is not preferable in the standpoint of environment. Moreover, when a resin layer (resin outer layer) is directly formed on the outer peripheral surface of the metal plating layer, adhesive force between the metal plating layer and the resin outer layer is weak, resulting in lack of reliability of a product (hose).